Combination switch and variable resistor system



Feb. 18, 1969 R. c. MILLER 3,428,887

COMBINATION SWITCH AND VARIABLE RESISTOR SYSTEM Filed April 28. 1966 F I G. l

INVENTOR. RONALD c. MILLER ATTORNEY.

United States Patent 9 Claims ABSTRACT OF THE DISCLOSURE -A spring loaded switch and variable resistor is shown having an arcuate impedance element contacted by a wiper arm which is spring loaded and urged toward the center of the element. Each end of the impedance element connects to a source of potential while the center thereof is connected to a reference potential and provided with a detent to disengage the arm from contact with the impedance element. Manual adjustment of the wiper 'arrn overcomes the urging of the spring for producing an increased or decreased output potential depending on the direction and amount of manual activation. The spring returns the wiper arm to the center of the impedance element when manual adjustment ceases.

The present invention relates to an electrical switch and, more particularly, to a switch which is mechanically biased toward an oil position and which closes an electrical contact when manually actuated for providing a potential across the closed contact that varies in proportion to the amount of manual actuation.

(1" here are several applications fior an electric switch, as described by the present invention. An example of one application is found in conjunction with a capacitance memory circuit. If it is desired to change or correct an electrical charge stored upon the memory capacitor, means must be provided that are capable of decreasing or increasing the potential across the capacitor for subsequently adjusting the charge thereon. In such an arrangement, the means that decrease or increase the capacitor charge must generally be eliminated from the capacitance memory circuit when that circuitry is not specifically under-going adjustment.

One object of the present invention, therefore, is to provide an electronic switch which is mechanically biased toward an opened position and which provides a voltage dividing arrangement when the mechanical bias is overcome by a manual adjustment.

Another object of this invention is to provide an electrical switch which is capable of raising or lowering the potential .within an electrical circuit when actuated and which has no effect on that circuit when the actuating force is removed.

A further object of the instant invention is to provide a nomally open electrical switch which responds to manual actuation by closing an electrical contact and providing a variable potential across the closed contact which is pro portionally responsive to the degree of manual displacement of the switch.

A still further object of the invention is to provide a manually actuated electrical switch which will return to its normally opened position in the absence of a manual actuating iorce.

Still another object of the present invention is to provide an electrical switch which is capable of producing an electrical signal for varying a utilizing device at a speed proportional to the amount of manual actuation of the electrical switch.

Other objects and many advantages of the present invention will be readily appreciated as the same becomes better understood when considered in connection with the accompanying specification and drawings, wherein:

'FIG. 1 is a top view showing one embodiment of an electrical switch of the present invention;

FIG. 2 is a side elevation showing the electrical switch;

FIG. 3 is a partial perspective view of the electrical switch showing the pivotally arranged wiper arm and resistive elements; and

FIG. 4 is a schematic representation of one application of the present invention.

(The electrical switch generally includes an impedance element consisting of a resistive layer attached to a base member of noncondu-ctive material. A pivotally arranged wiper arm assembly contacts the resistive layer of the base member and is urged toward the center thereof by a torsional spring. At the central position of base member the interaction of a detent raises a spring arm portion of the wiper arm assembly from a contacting position against the resistive coating for breaking the electrical contact therebetween. A thumb wheel is connected to the pivotally arranged wiper arm assembly for providing the manual actuation which displaces the spring arm from the detent onto the resistive layer of the base member. A source of potential is connected to each end of the nonconductive base member whereby contact between the spring arm and the resistive layer establishes a voltage dividing network. An example of one application for the electrical switch of the present invention is disclosed in a copending U.S. application, Ser. No. 433,875, filed Feb. 19, 196-5 by William Newbold. Here, the electrical switch is utilized in combination with a process controller having an automatic and manual mode of operation. When the process controller is switched firom automatic to manual operation, the controller continues to produce an output signal in the manual mode equalling the signal last produced in the automatic mode. This is achieved through the use of a memory capacitor circuit which stores a charge proportional to the signal last produced by the controller. When the controller is placed in the manual mode, the charged capacitor retains the controller output signal at its previous level. Adjustment of the controller output signal during the manual mode is accomplished by applying a variable potential across the memory capacitor through the utilization of the electrical switch of the present invention. In utilizing the electrical switch, it is desirable to prevent a previous adjustment of the manual mode from intluencing the process controller in the event the controller is switched from the manual mode to the automatic mode and back again. For this purpose the electrical switch is provided with a means fior mechanically biasing it toward a normally opened position. This arrangement eliminates the introduction of an unwanted signal to the process controller when that controller is switched from an automatic to a manual mode of operation.

Referring now to the drawings, and specifically to FIGS. 1 and 2, an electrical switch is shown generally at 10 having a base plate 12. One end of the base plate 12 is bent at a right angle to the plane of the base plate fior rfiorming an upwardly directed mounting end portion 14. A shoulder screw 16 passes through a spacer 18 and the mounting end portion 14 and is attached thereto by a lockwasher 20 and nut 22. A double ended torsional spring 24 slips over the shoulder screw 16 and is secured in a restrained condition by the combined action of the spacer 18 and the head of the shoulder screw 16. A spring retainer 26 is attached to the mounting end portion '14, as by rivets, for preventing the rotational motion of the spring 24.

The end of the base plate 12 opposite the end portion 14 is bent upwardly at a right angle to the plane of the base plate and then outwardly bent parallel to the base plate plane for forming a Z-shaped mounting portion 28.

A shaft 30 having an outwardly directed upper portion 32 is attached to the lower surface of the outwardly directed segment of the Z-shaped mounting portion 28, as by a flush rivet not shown. A thumb wheel 34 having a tubular shaped axially extending collar 36 is rotatably mounted upon the shaft 30 and retained thereon by a retaining ring 38. The thumb wheel 34 is provided with an annular groove 40 and a recess cavity 42 into which a cable 44 is introduced. A tubular member 46 is attached to the center of the cable 44, as by crimping, and is received by the recess cavity 42 for providing a rotational unity between the thumb wheel 34 and the cable 44. A retaining disk 48 is attached to the upper surface of the thumb wheel 34, as by bonding, for securing the cable 44 within the groove 40.

A pivotally arranged wiper arm assembly 50 is pivotally attached to the base plate 12 through the combined use of a pair of thr-ust bearings 52 and 54 and a shoulder pin 56 which passes through the bearings and the wiper arm assembly and attaches to the base plate 12, as by riveting. The thrust bearings 52 and 54 may be constructed from a low friction material such as polytetrafluoroethylene. Bearing 52 is permanently ai-fixed to the base plate 12, as by bonding, while the bearing 54 is slideably retained between the shoulder pin 56 and a pivotal member 58 of the wiper arm assembly 50. The pivotal member 58 has a ]-shaped cross section with a flattened base portion 60 which passes between the journal bearings 52 and 54 for providing the rotational supports of the wiper arm assembly 50. The upper portion of the pivotal member 58 extends back over the base portion 60 and parallel thereto for forming a bifurcated portion having arms 62 and 64 and also extends forward for forming a T-shaped portion 66. The double ends of the torsional spring 24 are retained on each side of the T- shaped portion 66 for urging the pivotally arranged wiper arm assembly 50 toward a central position. A pin 68 having a grooved portion 70 is attached to each arm 62 and 64 of the bifurcated portion of the pivotal member 58, as by riveting. Each end of the cable 44 is wrapped around pin 68, passing through the groove 70, and bent back upon itself where it is secured, as by the crimping of a tubular member 72. This completes the attachment of the thumb wheel 34 to the Wiper arm assembly 50.

An impedance element 74 is attached to the base plate 12, as by bonding. The impedance element 74, as best seen in FIG. 3, is constructed from a base member 76 of nonconductive material, such as phenolic, and is coated with a layer of resistive material 78. In the present embodiment the resistive material may be formed from a coating of a quick drying bonding agent having a sintered conductive material dispersed therein; an example of such a coating is varnish impregnated with carbon particles having a resistance of approximately 4500 ohms per inch when applied thinly over a nonconductive base. The nonconductive base member 76 is accurately formed having apertures in each end thereof for receiving a pair of eyelets 80 to which is connec ted a source of potential 82, as shown in FIG. 4. The ends of the arcuate base member and the central portion thereof are coated with conductive layers 84 and 85, respectively. In the present embodiment the conductive layers 84 and 85 are similar in form to the resistive layer 78 and are applied thereto by masking the resistive layer in the desired areas and placing the conductive material over the unmasked areas. One example of the conductive material forming layers 84 and 85 is a varnish impregnated with particles of silver having a resistance of approximately ohm per inch when thinly applied over the resistive layer 78. A tab portion 86, which is also coated with the conductive layer 85, extends laterally from the central portion of the arcuate base member 76 and is connected to a reference source, such as a zero potential or ground, through an eyelet 88. The eyelets and 88 are attached to the base member 76, as by curling, for establishing an electrical contact with the conductive layers 84 and 85. In the present embodiment the conductive material may be applied about the eyelets 80 and 88 after the attachment thereof to the base member 74 for increasing the electrical contact between the eyelets and the conductive layers 84 and 85. The presence of the conductive layer at the central portion of the arcuate base member 76 forms a pair of resistive elements 90 and 92 on each side of the base member 74.

A spring arm 94 is attached to the vertical portion of the J-shaped pivotal member 58 by means of a pair of screws 96 each passing through an insulating collar 98, the spring arm 94, and an insulating plate before being secured into the pivotal member 58 by threads therein. The collar 98 may be constructed from an insulating material, as for example acetal, and the plate 100 may be constructed from insulating material, such as polytetrafluoroethylene. A cylindrical detent 102 having a reduced lower portion, not shown, is mounted on the central portion of the arcuate nonconductive base member 76 with its lower portion passing therethrough and through the base plate 12 where it is attached, as by flush riveting. The detent 102 is formed from an insulating material, for example polytetrafluoroethylene. The spring arm 94 is constructed from a resilient material, as Phosphor bronze, having upwardly directed flanges 104 on each side of the arm tip. These flanges 104 engage the detent 102, as the arm rotates thereby, for lifting the arm 102 in an upwardly direction and thus removing a contact point 106 from contacting position against the resistive elements 90 or 92. The contact point may be fabricated from silver and is attached to the lower surface of the spring arm, as by soldering.

Wires, not shown, may be attached by soldering to the vertical portion of the spring arm 94 and the underside of the impedance element 74, at eyelets 80 and 88. This completes the electrical circuit between the impedance element 74 and the spring arm 94 and also the impedance element and the source of potential 82, as shown in FIG. 4.

In operation, if it is desired to provide a variable potential to a circuit, the thumb wheel 34 is manually rotated by the application of a rotational pressure to a knurled portion 108 on the outer periphery thereof. The displacement of the thumb wheel 34 causes the wiper arm assembly 50 to rotate about its shoulder pin 56 due to the torsional force applied thereto through the cable 44. As the wiper arm assembly 50 rotates, the spring arm 94 is displaced thereby dropping off the detent 102 and engaging the contact point 106 with the centrally located conductive layer 85 which is referenced to a zero potential. This closes the electrical contact between the impedance element 74 and the spring arm 94 and establishes a zero potential thereacross. As the spring arm 94 is further displaced, for example to the right as shown in FIG. 4, the contact point 106 engages the resistive element 92 for placing a negative potential across the arm and the central conductive layer 85. With increasing displacement of the spring arm 94, the negative potential also increases proportionally until the full negative potential of the source as applied across the arm 94 and conductive layer 85. Upon removal of the manual rotational pressure applied to the thumb wheel 34 the wiper arm assembly 50 will return to its central position due to the urging of spring 24. As the wiper arm assembly 50 returns to its central position, the spring arm 94 again engages the detent 102 thereby removing the contact point 106 and breaking the electrical connection with the impedance element 74 for returning the electrical switch to its normally opened position. In many applications it may be desirable to provide an indication of the amount of electrical switch displacement necessary for achieving the required adjustment. An example of such an indicator is shown in the form of a meter 110 illustrated in dotted outline in FIGS. 1 and 2.

In keeping with the objects of the present invention it is possible to modify the electrical switch shown and described hereinabove without departing from the scope of this invention. For example, the thumb wheel and cable arrangement may be replaced by a gear train; or this portion may be eliminated in its entirety thereby relying on the wiper arm assembly to provide the manual displacement of the spring arm. In another possible modification the laminated impedance element could be replaced with a single layered resistive element.

Accordingly, it may be seen that there has been provided an electrical switch having a normally opened switching arrangement capable of manual adjustment for establishing a voltage dividing network and which is capable of returning to its normally opened position in the absence of a manual adjustment. It has further been provided that the electrical switch may be manually adjusted for producing an output which is proportional with time, speed, and potential to the amount of manual actuation applied thereto.

Many modifications and variations of the present invention will become obvious to those skilled in the art in light of the above teachings, and it should therefore be understood that the embodiments described hereinabove are illustrations rather than limitations. Consequently, the present invention should be limited only by the appended claims.

What is claimed is:

1. An electrical switch comprising, resistive impedance means, a potential source connected to opposite ends of said impedance means, contact means for establishing a contacting relationship with said impedance means, means forming a predetermined position between opposite ends of said impedance means, means for urging said contact means toward said predetermined position on said impedance means, a reference source connected to said predetermined position on said impedance means for retaining said predetermined position at a potential whose value is less than the potential at one end of said impedance means and greater than the potential at the second end thereof, and adjustable means arranged for displacing said contact means from said predetermined position on said impedance means, against the force of said means for urging, toward one end or the other of said impedance means for establishing an output potential across said predetermined position and said contact means above or below said reference source.

2. The invention as set forth in claim 1 wherein said resistive impedance means comprises a nonconductive base member having a material of limited conductivity attached to portions of the surface thereof for forming at least one resistive element thereon.

3. The invention as set forth in claim 2 wherein said resistive impedance means comprises additionally said nonconductive base member being arcuately formed with said resistive elements attached thereto for forming said predetermined position on a central portion thereof, detent means for electrically disengaging said contact means from said impedance means mounted on said central predetermined position, and said contact means including pivotally arranged wiper arm means.

4. The invention as set forth in claim 2 comprising additionally, said resistive elements being a layer of resistive material disposed upon the surface of said nonconductive base member, a conductive layer disposed upon said resistive layer for forming said central predetermined position thereon, said potential source connected between oppositive ends of said nonconductive base member thereby maintaining a potential across said resistive layer, said reference source being connected to said conductive layer, whereby one end of said resistive layer upon said base member is maintained at a potential above said reference source potential and the second end of said resistive layer upon said base member is maintained at a potential below said reference source potential.

5. The invention as set forth in claim 1 wherein said contact means for establishing a contacting relationship with said impedance means comprises a pivotally arranged wiper arm means and said adjustable means comprises manually adjustable means connected to said wiper means.

6. The invention as set forth in claim 5 wherein said means for urging said wiper arm means toward predetermined position includes a torsionally wound spring.

7. The invention as set forth in claim 6 comprising additionally said wiper arm means including a spring arm for contacting said impedance means attached to a pivotal member having a bifurcated portion thereon oppositely disposed from said spring arm on opposite sides of the pivot point of said pivotal member, cable means connected to said bifurcated portion of said pivotal member, and said manually adjustable means including a thumb wheel member connected by said cable means to said bifurcated portion of said pivotal member.

8. The invention as set forth in claim 1 wherein said electrical switch additionally comprises, said resistive impedance means including a nonconductive base member having a layer of resistive material disposed upon portions thereof for forming at least one resistive element thereon, said contact means including a pivotally arranged wiper arm means, said adjustable means including manually adjustable means connected thereto for displacing said wiper anm means from a predetermined contacting position on said base member toward a resistive element thereon, said means for urging said wiper arm means toward said predetermined position on said base member being spring means active in the absence of a manual adjustment of said manually adjustable means, and said means for electrically disengaging said wiper arm means and said base member including a detent disposed for lifting said wiper arm means from said base member when said wiper arm means is urged toward and retained in said predetermined position by said spring means in the absence of said manual adjustment.

9. The invention as set forth in claim 8 wherein said electrical switch additionally comprises, said layer of resistive material disposed upon a common surface of said nonconductive base member for electrically joining opposite ends thereof for dropping said potential source thereacross, said predetermined position formed by a conductive layer disposed upon a centrally located portion of said resistive layer, said pivotally arranged wiper arm means including a spring arm for contacting said base member attached to a pivotal member having a bifurcated portion thereon oppositely disposed from said spring arm on opposite sides of the pivot point of said pivoted member, cable means connected to said bifurcated portion of said pivotal member, and said manually adjustable means including a thumb wheel member connected by said cable means to said bifurcated portion of said pivotal means, whereby manual actuation of said thumb wheel displaces said spring arm from said conductive layer onto said resistive layer for establishing electrical contact therebetween and creating a voltage dividing network.

References Cited UNITED STATES PATENTS 2,280,305 4/1942 Schauer 338-198 X 2,424,529 7/1947 Wimmer 338-215 2,618,724 11/1952 Vlahos 338l X 3,123,795 3/1964 Bender 338l72 3,205,466 9/1965 Youngbeck et al. 338l63 WARREN E. RAY, Primary Examiner.

US. Cl. X.R. 

